SIM cards can have their data protected by a PIN, or Personal Identification Number. If a user has enabled the PIN on their SIM card, the SIM will remain locked until the PIN is properly entered. Some phones provide the option of using a second PIN, or PIN2, to further protect data. If a user incorrectly enters their PIN number multiple times, the phone may request a PUK, or Personal Unblocking Key. The number of times a PIN must be incorrectly entered before the phone requests the PUK will vary from phone to phone. Once a phone requests a PUK, the SIM will remain locked until the PUK is correctly entered. The PUK must be obtained from the SIM's network provider. If a PUK is incorrectly entered 10 times the SIM will become permanently locked and the user must purchase a new SIM card in order to use the phone. In some cases the phone will request a PUK2 before it permanently locks the SIM card.